Steam and Gas Turbines Multiple Choice Questions on “Efficiencies”.
1. What does thermodynamic efficiency of steam turbine mean?
a) Ratio of power developed to the power that can be developed by ideal turbine
b) Ratio of power that can be developed by ideal turbine to the power developed by the actual turbine
c) Ratio of inlet temperature to outlet temperature
d) None of the mentioned
Answer: a
Clarification: Thermodynamic efficiency is the ratio of power developed by actual turbine to the power that can be developed by ideal turbine.
2. What does aerodynamic efficiency mean?
a) Energy that can be extracted from a given volume of steam at given temperature and pressure
b) Amount of steam turbine blade can allow to flow inside
c) Amount of energy contained in steam
d) None of the mentioned
Answer: a
Clarification: Aerodynamic efficiency means energy that can be extracted from given volume of steam at given pressure and temperature.
3. If efficiency of boiler increases then efficiency of steam turbine ______
a) decreases
b) increases
c) cannot be determined
d) none of the mentioned
Answer: b
Clarification: If the efficiency of steam boiler increases temperature also increases which indirectly increases its efficiency.
4. If condenser efficiency increases then overall efficiency of steam turbine _______
a) decreases
b) increases
c) remains constant
d) none of the mentioned
Answer: b
Clarification: If condenser efficiency increases it raises the steam temperature and hereby increasing overall efficiency.
5. What does combustion efficiency mean?
a) Boiler ability to burn the fuel to fuel that is not burned and amount of air present at exit
b) Calorific value that can be obtained by burning a fuel
c) Energy that is released when fuel is burned
d) None of the mentioned
Answer: a
Clarification: Combustion efficiency is used to denote the amount of fuel burned by using the air.
6. What does fluid to fuel efficiency mean?
a) It indicates the overall efficiency of the boiler
b) Indicates fuel efficiency
c) Overall efficiency excluding boiler efficiency
d) None of the mentioned
Answer: a
Clarification: Fluid to fuel efficiency indicates overall efficiency including Boiler efficiency, conduction, convection and radiation, etc.
7. The total energy in the fuel is called as _____________
a) boiler efficiency
b) boiler energy
c) gross calorific value
d) none of the mentioned
Answer: c
Clarification: Gross calorific value indicates the total energy a fuel can release when burned.
8. Flue gases _______ efficiency.
a) decreases
b) increases
c) does not effect
d) none of the mentioned
Answer: b
Clarification: Flue gases effect combustion of the fuels and due to that it affects the overall efficiency.
9. Nozzle efficiency can be defined by __________
a) ratio of kinetic energy of the steam leaving the nozzle to the potential energy available with the steam while entering
b) pressure of the steam leaving the nozzle to pressure of the steam entering the nozzle
c) temperature of the steam leaving the nozzle to the temperature of the steam entering the nozzle
d) none of the mentioned
Answer: a
Clarification: Nozzle is used to convert the potential energy of the steam available into kinetic energy to run the turbine.
10. What is the typical efficiency of the nozzle?
a) 0.45-0.56
b) 0.9-0.99
c) 0.5-0.7
d) 0.67-0.86
Answer: b
Clarification: The typical efficiency of the nozzle is between 0.9 and 0.99.